10. Boolean logic
A section of Computer Science, 0478
Listing 10 of 62 questions
Computers use logic gates. State the single logic gate that produces each truth table. Truth table Logic gate A B Output A B Output A B Output An aeroplane has a warning system that monitors the height of the aeroplane above the ground, whether the aeroplane is ascending or descending, and the speed of the aeroplane. Input Binary value Condition Height (H) Height is less than 500 metres Height is greater than or equal to 500 metres Ascending or Descending (A) Aeroplane is ascending or in level flight Aeroplane is descending Speed (S) Speed is less than or equal to 470 knots Speed is greater than 470 knots
0478_m21_qp_12
THEORY
2021
Paper 1, Variant 2
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A gas fire has a safety circuit made up of logic gates. It generates an alarm (X = 1) in response to certain conditions. Input Description Binary value Conditions G gas pressure gas pressure is correct gas pressure is too high C carbon monoxide level carbon monoxide level is correct carbon monoxide level is too high L gas leak detection no gas leak is detected gas leak is detected The output X = 1 is generated under the following conditions: gas pressure is correct AND carbon monoxide level is too high OR carbon monoxide level is correct AND gas leak is detected Draw a logic circuit for this safety system. * & ; / Complete the truth table for the safety system. G C L Workspace X Complete the truth table for the XOR gate: A B C
0478_s15_qp_12
THEORY
2015
Paper 1, Variant 2
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A computer-controlled machine produces plastic sheets. The thickness of each sheet must be within a certain tolerance. The sheets are kept below 50 °C as they move over rollers at 10 metres per second. Three parameters need to be monitored all the time. Parameter Description Binary value Conditions D sheet thickness thickness of sheet in tolerance thickness of sheet out of tolerance S roller speed roller speed = 10 metres/second roller speed <> 10 metres/second T temperature temperature = 50 °C An alarm, X, will sound if: thickness is in tolerance AND (roller speed <> 10 metres/second OR temperature >= 50 °C) OR roller speed = 10 metres/second AND temperature >= 50 °C Draw a logic circuit to represent the above monitoring system. D S X T Complete the truth table for the monitoring system. D S T Working Space X
0478_s16_qp_11
THEORY
2016
Paper 1, Variant 1
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A computer-controlled machine produces plastic sheets. The thickness of each sheet must be within a certain tolerance. The sheets are kept below 50 °C as they move over rollers at 10 metres per second. Three parameters need to be monitored all the time. Parameter Description Binary value Conditions D sheet thickness thickness of sheet in tolerance thickness of sheet out of tolerance S roller speed roller speed = 10 metres/second roller speed <> 10 metres/second T temperature temperature = 50 °C An alarm, X, will sound if: thickness is in tolerance AND (roller speed <> 10 metres/second OR temperature >= 50 °C) OR roller speed = 10 metres/second AND temperature >= 50 °C Draw a logic circuit to represent the above monitoring system. D S X T Complete the truth table for the monitoring system. D S T Working Space X
0478_s16_qp_13
THEORY
2016
Paper 1, Variant 3
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Questions Discovered
62